Power factor is generally used with regard to AC circuits irrespective of if it is single phase or three phase. Unlike AC circuits, in DC circuits one can simply determine the power by multiplying the readings of the voltmeter and ammeter connected in the circuit.
In AC circuits, the true power dissipated in the circuit cannot be determined just by multiplying the supply voltage and the load current, as it determines apparent power. To determine the true power, a wattmeter is introduced in the circuit to measure the true power. The ratio of active power to apparent power is called power factor.
Leading vs Lagging Power Factor
The main difference between Leading and Lagging Power Factor is that the leading power factor is used to describe the situation where the load current leads the supply voltage whereas the lagging power factor is used to describe the situation where the load current lags behind the supply voltage.
Also, the power factor always varies between 0 to 1. It can be determined by the lag or lead of load more in regard to supply voltage. The usage of the terms lagging and leading is decided by where the load current phasor lies in relation to the supply voltage phasor.
Comparison Table Between Leading and Lagging Power Factor
| Parameters of Comparison | Leading Power Factor | Lagging Power Factor |
|---|---|---|
| Definition | Leading Power Factor is a term which is used where the load current leads the supply voltage. | Lagging Power Factor is a term which is used where the load current lags behind the supply voltage. |
| Phase angle | In relation to the driving voltage phase angle, the resulting current phase angle is positive. | In relation to the driving voltage phase angle, the resulting current phase angle is negative. |
| Significance | Leading power factor in an AC circuit signifies that the load current is capacitive. | Lagging power factor in an AC circuit signifies that the load current is inductive. |
| Correction | To correct a leading power factor, inductive loads must be added. | To correct a lagging power factor, capacitive loads should be added. |
| Examples | Radio circuits, electric motors, power supplies are some examples of capacitive loads. | Repulsion induction motors, power generators, relays are some examples of inductive loads. |
What is Leading Power Factor?
Leading power factor is used to describe the situation where the load current leads the supply voltage. It is a property of an electric circuit that determines if the load current is capacitive. This means that if the load is capacitive, it will cause a lagging power factor in the circuit.
To correct a leading power factor, capacitive loads should be added to the circuit. A leading power factor means that at a low internal induced voltage, one can maintain the same terminal voltage. A positive power factor is the power factor of a leading current. It is sometimes called positive power factor.
The current that reaches its peak value that is 90 degrees ahead of the supply voltage can be generally described as leading power factor. Radio circuits, electric motors, power supplies are some examples of capacitive loads. To sum it up, to get a leading power factor, the load has to be capacitive.
What is Lagging Power Factor?
Lagging power factor is used to describe the situation where the load current lags behind the supply voltage. It is a property of an electric circuit that determines if the load current is inductive.
This means that if the load is inductive, it will cause a lagging power factor in the circuit. To correct a lagging power factor, capacitive loads should be added to the circuit. The most common form of three phase motors is the repulsion induction motor which is an inductive load and always has a lagging power factor.
To sum it up, to get a lagging power factor, the load has to be inductive. The current that reaches its peak value that is up to 90 degrees later then the supply voltage can be generally described as lagging power factor.
All the AC motors except the overexcited synchronous motors and transformers operate at lagging power factor. Repulsion induction motors, power generators, relays are some examples of inductive loads.
Main Differences Between Leading and Lagging Power Factor
- Leading power factor is used to describe the situation where the load current leads the supply voltage whereas lagging power factor is used to describe the situation where the load current lags behind the supply voltage.
- In relation to the driving voltage phase angle, the resulting current phase angle of leading power factor is positive while the resulting current phase angle of lagging power factor is negative.
- Leading power factor signifies that the load current is capacitive whereas lagging power signifies that the load current is inductive in an AC circuit.
- To correct a leading power factor, inductive loads must be added while to correct a lagging power factor, capacitive loads should be added.
- Radio circuits, electric motors, power supplies are some examples of capacitive loads while some examples of inductive loads are repulsion induction motors, power generators and relays.
Conclusion
Power Factor is the ratio of active power to apparent power in an AC circuit. Leading power factor is a term which is used where the load current leads the supply voltage whereas lagging power factor is a term which is used where the load current lags behind the supply voltage.
The usage of the terms lagging and leading is decided by where the load current phasor lies in relation to the supply voltage phasor. If the current phase angle is positive then it’s leading and if the current phase angle is negative then it’s lagging.
Leading power factor signifies that the load current is capacitive whereas lagging power signifies that the load current is inductive. Inductive loads are added to correct a leading power factor while capacitive loads are added to correct a lagging power factor.
References
- https://journals.sagepub.com/doi/pdf/10.1177/002072096500300414
- https://safetyclimate.sites.tamu.edu/wp-content/uploads/sites/96/2016/05/Payne-et-al.-2009-Safety-climate-Leading-or-lagging-indicator-of-safety-outcomes.